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From Danil Ε’ORIN <torin...@gmail.com>
Subject Custom Directory and IndexInput
Date Tue, 21 Aug 2012 06:22:09 GMT
I'm trying to build a custom directory implementation, actually the
directory itself just fallback to one of the existing directory
implementations, so it's actually more about IndexInput/IndexOutput.

I have some concerns about my implementation, especially related to
multithreading:

   - IndexOutput writeByte/writeBytes should be no problem since only one
   thread will write to specific output at any time
   - IndexInput on the other hand could be called from multiple threads
   - most implementations of IndexInput (including mine) keep some internal
   state like current position in the file/buffer/etc
   - if one of the threads is calling readShort()/readLong()/readVInt()
   (default implementations from DataInput) while some other thread is calling
   readByte() bad stuff will happen
   - still in most existing implementations I don't see any synchronization
   code on reads
   - is this problem solved somewhere on a higher level, like
   IndexReader/IndexSearcher, so I don't have to worry about it?
   - cause I'm really not sure how to solve it without forcing synchronized
   on all read methods and I'd really hate that.

How this issue is solved in Lucene? what should I do to make sure that my
implementation doing right thing?

Currently I'm on Lucene 4.0.0 BETA

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